The present invention relates to an optical apparatus having a driving source for driving a lens in an optical axis direction, and particularly, to an optical apparatus which includes a vibration type linear actuator for use as a driving source.
Some optical apparatuses include a vibration type linear actuator for use as a driving source for driving a lens (for example, see Japanese Patent Laid-Open No. 10(1998)-90584).
In the optical apparatuses proposed in Japanese Patent Laid-Open No. 10(1998)-90584 having the vibration type linear actuator, the vibration type linear actuator is formed of a vibrator which produces vibration through an electromechanical energy conversion action and a contact member which is in press contact with the vibrator. The vibrator is fixed to a lens holding member, the contact member is fixed to a stationary member of a lens barrel, and the vibrator is caused to produce driving vibration, thereby moving the lens holding member together with the vibrator, or the contact member is fixed to the lens holding member, the vibrator is fixed to the stationary member of the lens barrel, and the vibrator is caused to produce driving vibration, thereby moving the lens holding member together with the contact member.
The description will be made of the lens barrel proposed in Japanese Patent Laid-Open No. 10(1998)-90584 using FIGS. 17 and 18.
In FIGS. 17A to 17D, reference numeral 901 denotes a lens holding frame, 902 denotes a guide bar which guides the lens holding frame 901 in the optical axis direction. Reference numeral 904 denotes a vibrator, 905 a supporting portion which supports the vibrator 904, 906 a contact member which is in press contact with the vibrator 904, and 907 a biasing member which produces the press contact force acting between the vibrator 904 and the contact member 906.
In FIG. 18, reference numeral 911 denotes a lens holding frame, and 913 a guide bush which is attached to the lens holding frame 911 and engages with a guide bar 930 in a movable condition in the optical axis direction. Reference numeral 920 denotes a vibrator holding frame which is provided on the guide bush 913, and 925a and 925b supporting portions which support a vibrator 923. Reference numeral 922 denotes a contact member which is fixed to a lens barrel main body, and 926 a spring which produces the press contact force acting between the vibrator 923 and the contact member 922.
In a case where the press contact force between the vibrator 904, 923 and the contact member 906, 922 is provided by the biasing member 907 and 926 as shown in FIGS. 17A to 17D and 18, the reaction force of the press contact force acts on the engagement parts of the lens holding member 901, 911 and the guide bar 902, 930, and a lateral pressure according to the press contact force acts on the engagement parts. The press contact force in the vibration type linear actuator is extremely large, so that such a lateral pressure increases the friction in the engagement part, thereby increasing the driving load. This causes problems that an increase of the output power of the vibration type linear actuator is required, the engagement part is worn, and it becomes difficult to perform a fine and accurate lens drive.